The boards of Energy Transfer and Southern Union have approved the revised deal which was announced Tuesday.

"We have listened to Southern Union shareholders and are providing a superior yet simpler transaction, including a significant cash component and the opportunity to benefit from Energy Transfer's upside through the ownership of Energy Transfer common units," Energy Transfer Chairman Kelcy Warren said in a statement.

Warren is also Energy Transfer's biggest unitholder.

Energy Transfer said that the transaction includes a combination of cash and common units. Southern Union shareholders can exchange their stock for $40 per share or 0.903 Energy Transfer common units.

The maximum cash portion of the deal is 60 percent, while the common unit component may vary between 40 percent and 50 percent.

The announcement follows Williams' unsolicited $39-a-share all-cash bid, which was valued at about $4.9 billion in late June. Energy Transfer had initially offered $33 per share in stock, or $4.2 billion.

A Williams spokeswoman did not return a call seeking comment on Energy Transfer's latest offer.

Energy Transfer said that investors holding 14 percent of Southern Union shares have already signed agreements supporting its offer.

"This deal creates strategic benefits that could not be achieved through any other industry combination," Southern Union Chairman and CEO George Lindemann said. "Our businesses are highly complementary."

Energy Transfer, headquartered in Dallas, owns Energy Transfer Partners, which operates 17,500 miles of pipelines in several states. Southern Union, based in Houston, owns and operates 20,000 miles of pipelines.

Energy Transfer said its latest offer is worth $8.9 billion, including debt. The transaction is not subject to any financing contingency. Energy Transfer said it has lined up about $3.3 billion in committed financing from Credit Suisse to help pay for the cash portion of the acquisition.

Energy Transfer said it will sell some of its businesses, but did not disclose which ones, in order to make sure it receives federal antitrust approval for the proposed deal. The company anticipates closing the transaction in or before the first quarter of 2012.

In a separate transaction, Southern Union will sell its 50 percent stake in Citrus Corp. to Energy Transfer Partners LP for $1.9 billion in cash. Citrus owns the Florida Gas Transmission pipeline system. The sale is subject to the closing of Energy Transfer Equity's acquisition of Southern Union and is not subject to any financing condition or Energy Transfer Partner unitholder approval.